An exchangeable adapter is provided for reducing the size of a trash removal opening of an opening roller housing in open-end spinning arrangements. The said adapter comprises two semi-spherical supporting surfaces at a distance to one another for positioning the adapter on corresponding rounded countersurfaces. The adapter comprises further a curved fiber guiding surface corresponding to the curve of an opening roller as well as a boundary wall for reducing the size of the trash removal opening arranged directly upstream of the fiber guiding surface. The adapter is made from profiled bars and cut to the required effective width. The fiber guiding surface can be provided with a recess which is connected with the external atmosphere and which permits the entry of air into the opening roller housing.